1. Field of the Invention
This invention relates to a self-lubricating bearing and a method of producing the same, particularly to the self-lubricating bearing having a main body embedded with a plurality of solid lubricant pieces that have wear-resisting and lubricating functions, and the manufacturing method thereof.
2. Description of the Prior Art
Bearings are special objects for decreasing the wearing of components in performing relative motion. There are varied known bearings applied for different situations and designs. A known conventional self-lubricating bearing 1 capable of being sleeved on a relative-moving workpiece 10, as shown in FIGS. 1, 2 and 3, has a metallic main body 11 provided with an inner annular wall surface 111, an outer annular wall surface 112, a plurality of perforated holes 113 radially penetrating through the inner annular wall surface 111 and the outer annular wall surface 112, an outer oil groove 114, an inner oil groove 115, an oil hole 116 radially penetrating through the outer oil groove 114 and the inner oil groove 115, and a through hole 117 surrounded and defined by the inner annular wall surface 111 and capable of being sleeved by the relative-moving workpiece 10. A plurality of solid lubricant pieces 12 capable of being respectively inserted into the plurality of perforated holes 113 of the main body 11 are made of graphite added with MoS2 so as to have the functions of resisting wear and containing a lubricating oil. Each of the plurality of solid lubricant pieces 12 has a radial inside surface 121  in a curve conforming to that of the inner annular wall surface 111 and a radial outside surface 122 in a curve conforming to that of the outer annular wall surface 112.
A method of manufacturing such known conventional self-lubricating bearing 1 includes the steps of: forming the plurality of perforated holes 113, the outer oil groove 114, the inner oil groove 115 and the oil hole 116 on the main body 11; inserting the plurality of solid lubricant pieces 12 in a stick form respectively into the plurality of perforated holes 113 in which the stick-like solid lubricant pieces 12 are devised to have an outer diameter slightly smaller than an inner diameter of the plurality of perforated holes 113 for the convenience of being inserted into the perforated holes 113 easily; heating the combination of the stick-like solid lubricant pieces 12 and the perforated holes 113 to make the stick-like solid lubricant pieces 12 securely fixed in the perforated holes 113 in which the inside surfaces 121 and the outside surfaces 122 of the stick-like solid lubricant pieces 12 are slightly protruded out of the inner annular wall surface 111 and the outer annular wall surface 112 after heated; grinding the protruded inside surfaces 121 and the protruded outside surfaces 122 to make the inside surfaces 121 and the outside surfaces 122 respectively smoothly integrated with the inner annular wall surface 111 and the outer annular wall surface 112 of the main body 11, which is very complicated in such manufacturing processes.
Although such known conventional self-lubricating bearing 1 is devised to have the plurality of solid lubricant pieces 12 directly inserted into the plurality of perforated holes 113 of the main body 11 to achieve its basic requirement, such design has the following disadvantages:
1. Greatly increasing the material cost: 
The plurality of solid lubricant pieces 12 are inserted into the plurality of perforated holes 113 of the main body 11 with a depth the same as the thickness of the main body 11, which greatly increases the material cost. The cost of the solid lubricant pieces 12 is much higher than that of the main body 11. When the solid lubricant pieces 12 are worn off a depth of approximately 0.2 mm after being used in a period of time, the known conventional self-lubricating bearing 1 is required to be replaced with a new one because of serious accuracy deviation, which is also very wasteful.
2. Impossible to keep structural strength and lubricating effect simultaneously:
The plurality of perforated holes 113 penetrating through the main body 11 of the known conventional self-lubricating bearing 1 do bring a definite destruction to the whole structure of the main body 11, thus decreasing the structural strength of the main body 11. In fact, in order to increase the lubricating effect of the self-lubricating bearing 1, more spots with wear-resisting and lubricating functions are required to be arranged on the inner annular wall surface 111 of the main body 11, and this surely decreases the structural strength of the main body 11. On the contrary, in order to keep the structural strength of the main body 11, less spots with wear-resisting and lubricating functions are required to be arranged on the inner annular wall surface 111 of the main body 11, and this surely decreases the lubricating effect of the self-lubricating bearing 1. Therefore, it is impossible for the known conventional self-lubricating bearing 1 to keep structural strength and lubricating effect simultaneously.
3. The known conventional self-lubricating bearing 1 is manufactured with such complicated processes, which not only lengthens the working time, but also increases the total production cost. 